I do not think there is anything threatening about marches, period - hippie or otherwise. Those marches used to be threatening for the reason Karl Marx said they would be - they demonstrated the willingness to take a collective action by the people already unified by the relations of productions. Factory workers were already unified by the fact of working in factories owned by bourgeoisie - and by that very virtue they could grab the capitalists by the balls if they decided to act in concert. That is why capitalists they were scared of any demonstration of working class willingness to act in concert.
But these days are long gone and the working class unity is gone with it. A demonstration today is an empty threat because those who demonstrate cannot do what the industrial working class of the pervious era could - shut down the production and kick the capitalist class in their balls i.e. their wallets. The capitalist class knows darn well that all those who demonstrate in DC can do is to go home, bitch about the government, perhaps send a small donation to an organization of their choice and vote on someone else than the current asshole in DC, and if they are really pissed - smash a few windows and burn a few cars.
Neither of those actions is particularly threatening to capitalists because they learned to how to manage and control them. Donations to progressive organizations and politicians pale in comparison with truckloads of money forked over to conservative PACS and politicos by capitalists. Capitalists and their hit squats perfected the art of character assassination, so they know darn well what to do is someone tries to pull a Howard Dean on them. And window smashing? The police and the National Guard handle that quite competently, while the capitalists and their hacks gain new ammunition for their argument that the people who challenge the status quo are nothing but a bunch of thugs that cannot be taken seriously.
So marching of any kind has the zero effect on the capitalist class - its only value is to make the participants feel good about themselves and perhaps develop some sense of unity. That is important, but can be achieved though alternative, less costly and more effective means.
The only thing that would make capitalists scared is kicking them in their wallets - e.g. by creating alternative forms of economic activity e.g. social economy, cooperatives etc.
Wojtek